The long-term goal of the candidate's research program is to understand as completely as possible the neuronal basis of the entire behavioral repertoire of a simple invertebrate--the nematode worm C. elegans. To this end he has developed several important new techniques that have advanced the research goals of his and other labs. However, achieving a virtually complete account of behavior will require another new technique in C. elegans: optical recording of membrane potential from multiple neurons in intact, behaving animals. The candidate seeks release from teaching and reduced administration in order to develop molecular probes for membrane potential based on green fluorescent protein (GFP), and to use these probes to further the goals of his continuing research on the neuronal basis of spatial orientation behavior in C. elegans. The career development plan has four components. Component I is to coordinate and participate in a new consortium of three PI's and six consultants to re-engineer the FlaSh protein, a promising form of voltage-dependent GFP. The consortium brings together world leaders in structural biology, biophysics, fluorescent probes, and optical recording with the aim of enhancing the speed and sensitivity of the original FlaSh molecule. If successful, the re-engineered protein will be used to elucidate the neuronal basis of chemotaxis, a widespread form of spatial orientation, in the nematode C. elegans. The proposed research is significant because it will likely lead to new genetically targetable probes of neuronal activity that can be used in many other important experimental systems. In addition, this work will deepen our understanding of neural computations underlying a common goal-directed behavior. Components II and III are, respectively, technical courses and tutorial visits to laboratories at the leading edge of optical recording technology. These two activities will give the PI new technical background needed to complete the work of Component I. Component IV is a course the PI will teach in research ethics, drawing on his extensive background in analytical philosophy.